Design and synthesis of new steroidal inhibitors of estrogen synthase (aromatase)

First synthesis of 7α- and 7β-amino-DHEA, dehydroepiandrosterone (DHEA) analogues and preliminary evaluation of their cytotoxicity on Leydig cells and TM4 Sertoli cells

Efficient syntheses of new DHEA analogues, and their apoptotic and necrotic effects on Leydig cells and TM4 Sertoli cells are described. The key step in the synthetic strategy of 7-amino-DHEA derivatives involves a bromination on C-7 position to give an epimeric mixture of bromides which were substituted by azides and reduced to give 7alpha- and 7beta-amino-3beta-hydroxyandrost-5-en-17-ones. No cytotoxic effect induced by apoptosis mechanism was observed on Leydig and TM4 Sertoli cells by treatment with these amino-DHEA analogues. A necrotic effect was induced only in TM4 Sertoli cells. The best activity was obtained with 7alpha,beta-amino-androst-5-en-3beta-ol and 7beta-amino-3beta-hydroxy-androst-5-en-17-one.

Metabolic conversion as a pre-receptor control mechanism for lipophilic hormones

The majority of physiological effects mediated by steroids, retinoids and thyroids is accomplished by binding to members of the nuclear receptor superfamily of ligand activated transcription factors. The complex specific effects of lipid hormones depend not only on receptor expression, distribution and interactions, but also on the availability and metabolic conversion of the hormone itself. The cell-specific metabolic activation of inactive hormone precursors introduces a further level of hormonal regulation, and constitutes an important concept in endocrinology. The metabolic reactions carried out are achieved by dehydrogenases/reductases, hydroxylases and other enzymes, acting on ligands of the steroid/thyroid/retinoic hormone receptor superfamily. The concept implies that these tissue- and cell-specific metabolic conversions contribute to lipid hormone action, thus pointing to novel targets in drug development. All components of this signalling system, the hormone compounds, the receptor proteins, and modifying enzyme families originate from an early metazoan date, emphasizing the essential nature of all elements for development and diversification of vertebrate life.